Roof and inlets/outlets

[eandg]

Roof build up will likely be SIPs roof, 50mm cavity, 18mm ply below standing seam roof. Would venting the MVHR inlets/outlets to the cavity be sufficient or would it have to pierce the ply/standing seam? 

[Iceverge]

No to the cavity from me. 

 

You're likely to get off gassing from the roofing materials on sunny days  not to mention the ventilated space will get very hot in the sun. 

 

On a still summers day even with roof terminal unless you allow a significant inlet height you’re lightly to get elevated intake temperatures. 

 

Are wall terminals an option?

[Russell griffiths]

Definitely not. 

Why would you want to blow all that moist stale air out under your roof covering. 

 

Nope, 

[eandg]

8 hours ago, Russell griffiths said:

Definitely not. 

Why would you want to blow all that moist stale air out under your roof covering. 

 

Nope, 

 

I have no idea how much air it'll involve but thought it might be an issue hence asking the question. 

 

8 hours ago, Iceverge said:

No to the cavity from me. 

 

You're likely to get off gassing from the roofing materials on sunny days  not to mention the ventilated space will get very hot in the sun. 

 

On a still summers day even with roof terminal unless you allow a significant inlet height you’re lightly to get elevated intake temperatures. 

 

Are wall terminals an option?

Rooms are all vaulted ceilings so had presumed that it would need to be via roof for a bedroom and bathroom that doesn't share the gable wall. Will look into it now. 

[Russell griffiths]

Your fresh air in and stale air out will be via the plant room, not from the rooms that are being vented. 

Thats if I’m reading your post correctly, all rooms go back to a central location and then out doors from there. 

 

I think im reading it correctly as I just re read your original question where you say inlets and outlets, you only have one inlet and one outlet, not one per room. 

Edited May 10, 2021 by Russell griffiths

[Temp]

+1

 

If its a proper MVHR system the only two ducts to the outside are the inlet and outlet and both go to/from the heat exchanger unit.  Thats normally in the loft remote from bedrooms if possible. Ours is in the roof of a porch by the back door. Our Inlet and Outlet point vertically downwards under the eaves.  Keep the inlet well away from any boiler flue.

 

There are also ..

 

Fresh air inlet ducts from the heat exchanger to bedrooms and living rooms.

 

Stale air extraction ducts from the wet rooms (kitchen, bathrooms, WC) to the heat exchanger.

 

If you have a vaulted SIP roof some of these pipes may have to be visible internally? or perhaps hidden in boxing or behind a false wall? Some planning required.

 

 

[eandg]

Thanks both. Exchanger unit in the loft above the only bedroom which is not vaulted and can be vented on the gable wall. I had thought the ducts from rooms had to vent externally rather than were just through the internal plasterboard to pipework - misunderstanding on my part, sorry! Plan would be to hide pipework in the void between roof/insulation and plasterboard. 

[Russell griffiths]

Bear in mind your duct will be 92mm in diameter, unless you use the eye wateringly expensive oval stuff. 

[eandg]

23 minutes ago, Russell griffiths said:

Bear in mind your duct will be 92mm in diameter, unless you use the eye wateringly expensive oval stuff. 

Cheers. I have planned 100mm service could in ceilings (can lose the space with the vaulting) to account for that and presume/hope it's straightforward doubling up some batons to do so.